The present invention relates to a nozzle device for delivering a metalworking fluid to a precise location on a workpiece being metal worked, with the metalworking fluid comprising an amount of at least one oil-containing liquid and an amount of a non-flammable gas. The present invention further relates to a method for delivering such metalworking fluid in an amount sufficient to cool and lubricate the workpiece, while minimizing the amount of oil-containing liquid required.
It has been known for decades that metal, including aluminum, steel, and other types of ferrous and non-ferrous metals used for forming machines or parts, can be metal worked using various types of metalworking tools. More particularly, a metal workpiece is a piece of metal that can be metal worked to form a part or member. When a workpiece is metal worked without the benefit of a coolant or lubricant, the metalworking tool has a reduced work life. A shortened tool life increases the cost of metalworking. Also, without lubrication and cooling of the workpiece, metalworking a workpiece typically requires a longer cycle time. To reduce friction, extend the tool life, and reduce the time for metalworking, it has been known to use lubricants and/or cooling liquids to lubricate and/or cool the workpiece and the metalworking tool. Addition of these liquids extends the tool life and results in a more efficient metalworking process, i.e. improved surface texture of the metal worked product and increased metalworking process speeds and feeds. It is in the use and disposal of these metalworking fluids that problems are encountered and costs incurred rather than avoided. Typical problems lie in the areas of application methods, worker exposure, waste disposal, foaming, and the requirement for secondary workpiece cleaning operations.
Currently, various types of metalworking fluids are applied to workpieces, with the metalworking fluids designed to serve a variety of functions. Such functions include, but are not limited to, removal of heat from the workpiece and tool (cooling), reduction of friction among chips, tool and workpiece (lubrication), and removal of metal debris produced by the metalworking operation. The metalworking fluids are more particularly intended to act at the interface between the tool and workpiece.
Common metalworking fluids fall into two broad categories: oil-based and water-based fluids. Oils are typically used as lubricants, often at cutting speeds below 400 sfpm. Oil-based lubricants can be further classified as natural oils, synthetic oils, and semi-synthetic oils. These fluids tend to provide excellent lubricity and exhibit very good extreme pressure (EP) properties, but do not generally act as efficient heat transfer media. Water-based fluids are typically used as coolants, usually at cutting speeds above 400 sfpm. These fluids carry thermal energy from the tool/work interface very efficiently, and can be tailored to a specific application easily with the addition of additives which improve lubricity, inhibit rust, retard bacteria growth, and improve EP performance. Water-based fluids, however, tend to be inferior to oil-based fluids in terms of lubricity. Emulsions and water-soluble oils are sometimes used in an attempt to combine the most attractive properties of both oil-based and water-based metalworking fluids.
The metalworking fluid, regardless of specific type, is applied typically by either a flood application, a spray application, or a mist application. In flood application, a high volume liquid stream is directed into the metalworking zone. The high volumetric flow rate of this stream is a primary mechanism by which chips and thermal energy are carried away from the tool/workpiece/chip interfaces. The removal of hot chips is a major factor in maintaining the tool and workpiece at an acceptable temperature. If this is achieved, tool life is improved and unwanted changes in the mechanical properties of the workpiece due to temperature increases in the heat affected zone are minimized. Rapid removal of chips from the metalworking zone also reduces scoring of the metalworked surface, promoting good surface texture on the metal worked part. In addition, lubrication is provided by the high volumetric flow rates helping to carry fluid into the tool/workpiece and tool/chip interfaces. However, the flooding method can be quite expensive. Also, much of the metalworking fluid is not consumed during the metalworking process and, consequently, is either wasted or must be recovered and recycled. Recycling, however, can be expensive because the shavings or filings from the metalworking process must be separated from the metalworking fluid. Flooding is further problematic because it can result in potentially harmful worker exposure and waste disposal issues.
Mist application, in which the coolant/lubricant is delivered to the metalworking zone in the form of fine, airborne droplets, is well suited to operations in which the cutting or machining speed is high and the area of cut is low, e.g. end milling. Misting is often used in situations where flooding is impractical and can be advantageous because a lesser amount of liquid is used during the metalworking process which, in turn, means less wasted liquid. The spray method of application is similar to mist application, except the droplets in spray application are much larger than those in the mist method of application. A major disadvantage of each of these application methods is the potential for the exposure of the metalworking operator to harmful amounts of metalworking fluid.
Worker exposure to metalworking fluids can be hazardous to worker health due to inhalation and ingestion of the metalworking fluid, and skin exposure leading to dermatitis. Droplets of metalworking fluid, particularly in misting applications, are readily inhaled by the workers. Eventually, the inhaled metalworking fluid can cause severe respiratory health problems. In order to reduce worker exposure, misting is often conducted in a hooded assembly to ensure proper ventilation and removal of the metalworking fluid droplets. This can result in an increased cost associated with such application.
As mentioned, many currently used organic-based metalworking fluids are classified as hazardous waste materials. For this reason, it is desired to have a non-hazardous metalworking fluid for use in metalworking operations. Because of environmental, health, and cost issues, it is also desired to have a device or method that allows for the application of metalworking fluids to a workpiece whereby a lower fluid volume is required. It is further desired for the metalworking fluid to be non-hazardous to the health of the workers who are metalworking the various workpieces. It is most desired if the metalworking fluid, when applied to the workpiece, is consumed during the metalworking operation so that very little waste of the fluid occurs. It is further desired for the process to be economical.
Prior to the present invention, it was believed difficult to accurately apply a small volume of metalworking fluid to a workpiece while obtaining sufficient cooling and lubrication. Prior to the present invention, if a small amount of liquid was applied, generally, adequate cooling would not result. Also, directing the metalworking fluid to the right location, the interface, was difficult.
A metalworking fluid has now been discovered that is biodegradable, nontoxic, and poses no worker health hazards. A nozzle device for delivering a metalworking fluid to a precise location on a workpiece being metal worked, and a method for delivering such metalworking fluid in an amount sufficient to cool and lubricate the workpiece, while minimizing the amount of oil-containing liquid required has also been discovered.
It is an object of the present invention to provide a nozzle device and a metalworking method using the nozzle that precisely delivers a metalworking fluid to the tool/workpiece interface in an amount sufficient to cool and lubricate the workpiece while substantially eliminating the need to recover or dispose of used metalworking fluid. Elimination of waste is advantageous because environmental concerns are reduced, and the metalworking operation becomes more economical. In addition, use of less oil-containing liquid improves economic efficiency of the metalworking operation. It is a further object of the present invention to provide a nozzle device and a metalworking method using the nozzle which reduces worker exposure to metalworking fluids that can be hazardous to worker health due to inhalation and ingestion of the metalworking fluid, and skin exposure leading to dermatitis. It is yet a further object of the invention to provide a biodegradable, non-toxic metalworking fluid for use in the metalworking method of the present invention.
The present invention relates to a device and a method, each directed towards delivering an amount of metalworking fluid to a workpiece and metalworking tool so as to cool and lubricate both the workpiece and the tool, most preferably at the tool/workpiece interface. The device for delivering such fluid is a nozzle having a construction whereby oil-containing liquid and non-flammable gas can be inter-mixed to form a cooling and lubricating metalworking fluid. The nozzle can have a variety of different constructions, as long as there is an opening in the nozzle for receiving an amount of oil-containing liquid and an opening for receiving a pressurized non-flammable gas. Additionally, the nozzle includes a chamber or passageway whereby the oil-containing liquid and non-flammable gas can be mixed to form the metalworking fluid. The nozzle should further include a construction whereby the fluid exits through a narrow passageway to permit accurate placement of the metalworking fluid on a workpiece. When in use, the non-flammable gas and oil-containing liquid are mixed in the nozzle and then projected away from or passed through the nozzle, onto the interface between the workpiece and the metalworking tool member. The non-flammable gas will function to cool the tool and workpiece, and the oil-containing liquid will lubricate the interface therebetween. The non-flammable gas will enter the nozzle under a sufficient pressure to mix with the oil-containing liquid and be projected in a stream away from the nozzle such that the non-flammable gas and oil-containing liquid, i.e. metalworking fluid, hit at a precise point. Such precision is necessary to ensure that comparatively small amounts of oil-containing liquid are used and to ensure that the point where the greatest amount of friction and heat are generated will be cooled and lubricated.
In one embodiment, the nozzle will include at least a two part construction whereby a valve body and a tip are attached to one another. Another member that may be included in the nozzle construction is a hollow needle fitted into the valve body and projecting away from the valve body into a chamber found in the tip. The oil-containing liquid and non-flammable gas will enter the valve body and emanate from sources connected to the nozzle by a conduit or similar structure.
The method includes the steps of mixing non-flammable gas and oil-containing liquid to form the metalworking fluid. Further, the method includes the step of accurately delivering the metalworking fluid onto a precise location so as to cool and lubricate the tool and the workpiece at the tool/workpiece interface and ensure that most of the oil-containing liquid is consumed during the metalworking process.